Basic Colonoscopy
Mishita Goel, MBBS
Rajesh Keswani, MD, MS
Colonoscopy permits the visual examination of the mucosal surface from the anal canal to the terminal ileum using a flexible digital instrument. A coordinated series of maneuvers are required for safe intubation of colon and associated diagnostic and therapeutic manuevers, such as polypectomy. The acquisition of these skills requires dedicated training, often obtained during a standardized training program such as a gastroenterology fellowship. Besides providing the ability to visualize suspected colon abnormalities (e.g., inflammation), it also permits biopsy and therapy (e.g., polypectomy) at any site; the ability to acquire tissue for histopathologic analysis allows for a confirmatory diagnosis to be made (e.g., inflammatory bowel disease). In contrast, other noninvasive imaging tests are unable to obtain biopsies or perform therapy and thus have a purely diagnostic role.
INDICATIONS1
The indications of colonoscopy are myriad including both diagnostic and therapeutic. Screening and surveillance are the most frequent indications for colonoscopy.
Diagnostic, Including
a. average-risk persons generally beginning at age 50 years, every 10 years
b. if one first-degree relative diagnosed with colorectal cancer (or adenoma) at
i. age >60 years: beginning at 40 years, with subsequent examination intervals based on initial colonoscopy findings
ii. age <60 years: beginning at 40 years or 10 years before age of diagnosis of youngest relative, then every 5 years (also applies if two first-degree relatives diagnosed with colorectal cancer or adenomas)
c. Lynch syndrome: beginning at age 20 to 25 years, every 1 to 2 years, until age 40 years, then annually
d. Patients with familial adenomatous polyposis and identified colon polyps in whom surgery is being delayed: every 6 to 12 months
e. Women with endometrial or ovarian cancer diagnosed at age <50 years: beginning at time of diagnosis, then every 5 years
2. Evaluation of gastrointestinal bleeding:
a. Hematochezia (bright red blood per rectum) in absence of any definite anorectal source
b. Melena (black, tarry stools) after an upper source has been excluded
c. Iron-deficiency anemia
3. Positive fecal immunochemical test (FIT) (when FIT is used for colorectal cancer screening)
4. Evaluation of an abnormality on barium enema, flexible sigmoidoscopy, or CT colonography (virtual colonoscopy)
5. Surveillance:
a. after removal of adenomas or serrated polyps
i. US guidelines call for a 3-year interval examination in patients with three or more adenomas or when adenomas are >1 cm, contain high-grade dysplasia, or villous elements
ii. US guidelines recommend a 5-year interval examination in patients with one to two adenomas
iii. Guidelines vary when serrated polyps are removed during colonoscopy
b. When colonoscopy is accompanied by an inadequate preparation, a repeat colonoscopy is recommended within a year regardless of findings
c. after resection of colorectal cancer
6. In patients with ulcerative pancolitis or Crohn colitis of ≥8 years duration or left-sided colitis ≥15 years duration
7. Clinically significant diarrhea of unexplained origin
8. Evaluation for synchronous or metachronous malignancy in patients with colon cancer
9. Intraoperative lesion localization (e.g., polypectomy site, location of a bleeding site, or small mass)
Therapeutic, Including
1. Excision of precancerous colorectal lesions (i.e., polypectomy)
2. Hemostasis of bleeding lesions
3. Balloon dilation of strictures
4. Foreign body removal
5. Decompression of colonic pseudo-obstruction (Ogilvie syndrome) or volvulus
6. Endoscopic placement of a stent for a colorectal cancer causing large bowel obstruction
7. Percutaneous endoscopic cecostomy tube placement
CONTRAINDICATIONS
Absolute
1. Toxic megacolon
2. Fulminant colitis—Acute severe colitis characterized by toxic symptoms such as fever, anorexia, abdominal pain, diarrhea with shock or hypotension, ileus, or megacolon5,6
3. Known/suspected colonic perforation (however, if a colon perforation is caused during colonoscopy, colonoscopy may be continued to close the perforation)
Relative
2. History of recent myocardial infarction or pulmonary embolus
3. Cardiopulmonary instability
4. Suspected poor bowel preparation
Although not a contraindication to colonoscopy, patients with coagulopathies (either due to intrinsic disease or medications) require a personalized approach to colonoscopy to determine appropriateness of procedure and whether the coagulopathy needs to be corrected.
Colonoscopy can safely be performed in pregnancy, but the potential risks and benefits should be carefully considered.
PREPARATION9
1. Patient instructions—Informed consent must be obtained after explaining the procedure, its benefits, risks, alternatives, and limitations in an understandable format. It is recommended that written instructions be provided at least a week prior to the procedure so that the patient can read them all and follow the medication and dietary changes required.
2. Diet and medications:
a. Patients are recommended a low-residue diet for 2 to 3 days prior to colonoscopy
b. On the prior to the colonoscopy, either a clear liquid-only diet or a strict low-residue diet is appropriate
c. Most medications may be continued up until the time of colonoscopy
d. Diabetic medications require an individualized approach in coordination with the prescribing provider as blood sugars fluctuate with the altered diet
e. Iron must be stopped at least 5 days before colonoscopy since iron makes the residual feces black and difficult to purge
f. Whether anticoagulant medicines are continued or stopped is an individualized decision based on the indication for the medicines and the intervention planned. Aspirin can always be continued for colonoscopy. NSAIDs should be discontinued if possible as they may result in colon erosions/ulcers
g. Antibiotic prophylaxis is not required during colonoscopy
3. Labs—Routine preprocedure lab testing, chest imaging, or EKG is not required but may be used selectively based on patient’s medical history and physical examination.
4. Bowel preparation—An excellent bowel preparation is required for effective colonoscopy. The ideal bowel preparation is safe, efficacious, palatable, and affordable. Multiple FDA-approved bowel preparations exist10,11 like polyethylene glycol-electrolyte solutions (PEG-ELS),12 low-volume PEG-ELS, sulfate-free PEG-ELS, sodium phosphate13 etc., details of which are mentioned in Chapter 3.Related posts:
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